1. 1 CS 106 Computing Fundamentals II Chapter 21 “Computer Organization” Herbert G. Mayer, PSU CS Status 7/9/2013 Initial content copied verbatim from CS 106 material developed by CS professors: Cynthia Brown & Robert Martin

2. 2 Syllabus Nature of Data Nature of Data Computer Organization Computer Organization What Makes a Computer? What Makes a Computer? Computer Modules Computer Modules Instruction Set Architecture Instruction Set Architecture Bits, Moving Bits Bits, Moving Bits OS OS Applications Applications

3. 3 Nature of Data Spreadsheets give us a way to create processes that manipulate dataSpreadsheets give us a way to create processes that manipulate data We can think of a piece of data as a quantity that can be stored in a cell of a worksheetWe can think of a piece of data as a quantity that can be stored in a cell of a worksheet That cell represents an identifiable, physical location where the data residesThat cell represents an identifiable, physical location where the data resides What happens when you work on a spreadsheet or other programWhat happens when you work on a spreadsheet or other program

4. 4 Computer Organization (1) A typical computer is made up of a few basic parts:A typical computer is made up of a few basic parts: Processor. This is the “chip” where the work gets doneProcessor. This is the “chip” where the work gets done Might be an Intel chip or AMD or some other kind. Modern chips have multiple processors (“cores”) on them that can share the workMight be an Intel chip or AMD or some other kind. Modern chips have multiple processors (“cores”) on them that can share the work Modern computers have yet another processor for graphics processingModern computers have yet another processor for graphics processing A measure of chip quality is the speed, measured in Gigaherz. The bigger number means faster work! Does it matter? We wait anyway A measure of chip quality is the speed, measured in Gigaherz. The bigger number means faster work! Does it matter? We wait anyway  Amount of heat (in Watts) generated is criticalAmount of heat (in Watts) generated is critical

5. 5 Computer Organization (2) Memory. This memory is like the memory on a microwave; when the computer is off or loses power, the memory loses its contents (the way your microwave forgets what time it is when you have a power outage)Memory. This memory is like the memory on a microwave; when the computer is off or loses power, the memory loses its contents (the way your microwave forgets what time it is when you have a power outage) Memory is fast and is connected closely with the processor. Yet memory speed is slow in relation to the CPUMemory is fast and is connected closely with the processor. Yet memory speed is slow in relation to the CPU Memory speed is often measured in Megaherz; faster is better. The size of memory is measured in Gigabytes; 4 on 32-bit computersMemory speed is often measured in Megaherz; faster is better. The size of memory is measured in Gigabytes; 4 on 32-bit computers Storage, implemented as: disks, SSDs, or flash drivesStorage, implemented as: disks, SSDs, or flash drives Flash storage holds its value when the power is off, but is slower than regular memory. Size could be GigabytesFlash storage holds its value when the power is off, but is slower than regular memory. Size could be Gigabytes

6. 6 Computer Organization (3) Cache. This is a special-purpose memory that mediates between working memory and the processor. Having a good-size cache can make the computer faster. Caches are fast, yet expensive, consume more powerCache. This is a special-purpose memory that mediates between working memory and the processor. Having a good-size cache can make the computer faster. Caches are fast, yet expensive, consume more power Input devices. Keyboard, mouse, and microphone but also game controllers, laboratory instruments, etc.Input devices. Keyboard, mouse, and microphone but also game controllers, laboratory instruments, etc. Output devices, such as screen, printer, speaker, and others, like robot arms or a car’s brake systemOutput devices, such as screen, printer, speaker, and others, like robot arms or a car’s brake system

7. 7 What Makes a Computer? Many modern appliances have built-in chips; e.g. cars, televisions, washing machines, etc.Many modern appliances have built-in chips; e.g. cars, televisions, washing machines, etc. What makes a computer special is that it stores its program in memory, just like data, and can accept and execute new programsWhat makes a computer special is that it stores its program in memory, just like data, and can accept and execute new programs It can also potentially modify its own programs (“learn”)It can also potentially modify its own programs (“learn”)

8. 8 Computer Modules

9. 9 Instruction Set Architecture

10. 10 Bits Bit: Short for BInary digiTBit: Short for BInary digiT Everything in the computer, whether it is text, numerical data, music, videos, programs like Excel, macros or other code you write, or the operating system (Windows, MacOS, OSX, Linux) is stored digitally in these bits, tiny devices that have two distinct physical statesEverything in the computer, whether it is text, numerical data, music, videos, programs like Excel, macros or other code you write, or the operating system (Windows, MacOS, OSX, Linux) is stored digitally in these bits, tiny devices that have two distinct physical states Abstractly these states are represented by the numbers 0 and 1. Such an individual 0 or 1 container is the bitAbstractly these states are represented by the numbers 0 and 1. Such an individual 0 or 1 container is the bit

11. 11 Moving bits, Simplistic Model It would be too inefficient for the computer to access and move bits individually, though bit-based computers have been designed, e.g. NCR successor of Century seriesIt would be too inefficient for the computer to access and move bits individually, though bit-based computers have been designed, e.g. NCR successor of Century series Bits are grouped into chunks that are moved around the computer, from the disk to the memory to the CPU, as a groupBits are grouped into chunks that are moved around the computer, from the disk to the memory to the CPU, as a group The bigger the chunk is, the faster the computer can move data. A “32 bit” computer moves data in 32 bit chunks. A “64 bit” computer moves data in bigger 64-bit chunks and can conveniently handle a bigger working memoryThe bigger the chunk is, the faster the computer can move data. A “32 bit” computer moves data in 32 bit chunks. A “64 bit” computer moves data in bigger 64-bit chunks and can conveniently handle a bigger working memory The original chunk was typically a byte (8 bits)The original chunk was typically a byte (8 bits) Note that bus width and natural data width are orthogonalNote that bus width and natural data width are orthogonal

12. 12 Operating System The operating system is the key system SW on your computer: it controls what happens, and manages resources. If you have multiple programs open, for example, and you type something, it figures out where the characters should goThe operating system is the key system SW on your computer: it controls what happens, and manages resources. If you have multiple programs open, for example, and you type something, it figures out where the characters should go While the computer is up and running, the operating system is resident in working memory, to be fastWhile the computer is up and running, the operating system is resident in working memory, to be fast But when the computer is turned off… the memory is wiped outBut when the computer is turned off… the memory is wiped out So when you turn your computer on, how does it get started with no operating system?So when you turn your computer on, how does it get started with no operating system?

13. 13 “Booting” A special, dedicated device = chip that retains its data when power is off, has a small program built inA special, dedicated device = chip that retains its data when power is off, has a small program built in When you turn on your computer this program loads the actual operating system from the external memory into the working memoryWhen you turn on your computer this program loads the actual operating system from the external memory into the working memory This is called “booting” because it is supposedly like picking yourself up by your own bootstrapsThis is called “booting” because it is supposedly like picking yourself up by your own bootstraps This is what is going on during the minutes (on Windows) after you turn on the computer before your operating system shows upThis is what is going on during the minutes (on Windows) after you turn on the computer before your operating system shows up

14. 14 Applications Besides your operating system and some associated programs, your computer also has application programs that actually do the things you want to do: word processing, games, spreadsheets, play music, etc.Besides your operating system and some associated programs, your computer also has application programs that actually do the things you want to do: word processing, games, spreadsheets, play music, etc. The typical computer user just uses applications. In this class we will be creating some applications inside of ExcelThe typical computer user just uses applications. In this class we will be creating some applications inside of Excel

15. 15 1986 Cray 2 Supercomputer